The toe of the front wheel of an automotive vehicle is defined generally as the angular relationship of the principal plane of the front wheel to the vertical plane passing through the longitudinal axis of the vehicle. The provision of toe is essential to good stability and handling of the vehicle, and a proper life span of the tire carried by the wheel. A number of toe in devices have been developed for applying toe to the front wheels of automotive vehicles, but, by and large, existing devices are subject to the disadvantage of providing inaccurate results if the devices are disturbed from an initial position during the toe in adjustment procedure.
Thus, and using one currently popular type of toe alignment device as representative, the operator of the device is required to locate the device absolutely horizontal prior to toeing the wheel, and to maintain the device absolutely horizontal during the toe in procedure in order to be assured of achieving accurate results. Many such devices include a spirit level for the purpose of assuring maintenance of the toe in device in a horizontal position.
One substantial difficulty with this type of device is that, as a practical matter, it is almost a physical impossibility to maintain the alignment device absolutely horizontal during the toe in procedure.
For example, the operator must invariably strike one or more heavy blows against components in the suspension system of the vehicle in order to assure movement of the wheel into the proper, toed position. As can be readily appreciated, such blows can, and do, displace the toe in device which is attached to the wheel from its required perfectly horizontal orientation, with the result that inaccurate readings are obtained. As a consequence, the operator may believe the wheel is properly toed when the fact is it is not due to the error introduced by disturbance of the device from its original reference orientation.